1. Field of the Invention
This invention generally relates to integrated circuit (IC) fabrication and, more particularly, to a method for controlling printed ink line widths using fluoropolymer templates.
2. Description of the Related Art
Printed electronics fabrication relies on the application of metal precursor ink formulations to produce conductive circuit elements. These metal precursor inks are applied to a substrate by inkjet printing for example, and further processing steps are required to render the printed pattern conductive. Printed metal inks, however, produce conductive lines that have conductivities that are typically on the order of 10× less conductive than bulk metals or vacuum processed thin film metal layers. This inferior conductivity is detrimental to circuit design. The conductivity limitations of these materials can be traced to density limitations due to voids and film porosity, as well as grain size and interface effects. These detrimental effects can be reduced by increasing annealing time and temperatures. However, substrate and high temperature incompatibility of other thin film layers typically constrain the annealing time/temperature conditions that are suitable. For these reasons, increasing the conductivity of printed metal lines is challenging.
One means of increasing the conductance of a printed line is by increasing the cross-sectional area of that line. This result can be achieved by increasing the width and/or the height of the line. An increase of the width of a conductive line is not typically preferred because that line will consume more substrate area and result in fewer circuits that can be physically placed on a given substrate. Increasing the height of a printed line is conventionally the method used to increase conductance. However, with solution process, and printed conductive lines in particular, this is not easily achieved. Printing thicker lines by applying more ink or printing multiple passes of ink typically results in thicker lines, but also wider lines as the ink tends to spread on the substrate.
It would be advantageous if there was a method that added significant thickness to a printed conductive line, without an increase in line width.